Download What are viruses? - Northern Highlands

Honors Biology
Chapters 10, 16, 24
What are Bacteria?
• Bacteria are PROKARYOTES
– The smallest known living cells
Most are 0.1-0.5 mm in size
Bacteria on
head of a pin
Starr, 317
Did you know? There are over 80
species of bacteria in your mouth!
They are found
everywhere!
Bacteria in dental plaque
microbeworld.org
Some cause disease
We call these “pathogens”
Anthrax, as seen by Koch
microbeworld.org
But most are
beneficial
Bacteria ferment cheese
Schraer, 641
Structure of
Bacteria
Capsule (in some), jelly or slimy coating outside the
cell wall, for protection
Chromosome is single, circular, in nucleoid area
Plasmids (in some) tiny rings of DNA separate from
the chromosome.)
Pili extensions of the cytoplasm, help them talk to
other cells.
A prokaryote as it appears in a transmission electron microscope
Nucleoid
Many can MOVE, or go DORMANT
Some have flagella - made of
rope-like proteins, not
microtubules.
Some slide on a slimy secretion.
Endospore inside cell
Many can form dormant
cells called endospores
(chromosome in a strong shell)
to survive harsh conditions.
- tetanus, anthrax
Three basic
shapes
• Spherical – coccus
• Rod – bacillus
• Coiled - spirillum
Schraer, 633
Simple Colonies
Staphylo = clusters
Strepto = chains
Staphylococcus
wisc.edu
Streptobacillus
Diplo = double
Diplococcus
cat.cc.md.us
Cell Respiration in Bacteria
• OBLIGATE AEROBES
– must have oxygen to survive
• OBLIGATE ANAEROBES
– Cannot live in oxygen
– fermentation
• FACULTATIVE ANAEROBES
– Do either aerobic or anaerobic respiration
• Anaerobes make many fermentation products:
- foods (yogurt, cheeses, vinegar,. . )
- acids, alcohols, methane gas
Asexual Reproduction
Binary fission
1) chromosome replicates
2) copies separate as cell
wall lengthens
3) cell membrane pinches in
4) cells divide
Bacillus dividing by fission
See Fission in Action
Did you know? In ideal conditions, some
bacteria can divide every 20 MINUTES.
What stops them?
They run out of food or space,
or wastes build up and poison them.
Sexual Reproduction
conjugation
• Two bacteria connect
• Donor copies & passes
DNA to recipient
• Recipient now has new
genes
Ex.: Antibiotic resistance!!
Two bacteria in conjugation
Two more “sexual” reproductions
1. TRANSDUCTION
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•
virus inserts DNA
Bacterium now has new genes
2. TRANSFORMATION
•
•
Bacterium takes in plasmids or DNA fragments
from environment
Now has new genes
Sexual reproduction in bacteria
Two kinds of bacteria
• Domain Bacteria
– Kingdom Eubacteria (eu = “true”)
– Common, widespread bacteria
• Domain Archaea
– Kingdom Archaebacteria (archae = “ancient”)
– extremophiles
Kingdom Eubacteria
Many decomposers
Nitrogen suppliers
Some autotrophs
Some pathogens
Decomposers (saprobes)
•
•
Essential to nutrient cycling
Many live in soil
– Return inorganic chemicals to soil
– Plants take up chemicals to make food
•
Some live inside animals
– enterobacteria
– break down waste, make vitamins
E. Coli
Nitrogen-fixing Bacteria
“Fix” nitrogen = change nitrogen gas (N2)
from the air into a form plants can use
- Nitrogen – for proteins & nucleic acids
- Bacteria live in soil and in legume plants
clover, peanuts, soybeans, …
Legume roots – nodules contain
nitrogen-fixing bacteria
Photosynthetic bacteria
Cyanobacteria
•Have blue and green
pigments
•chlorophyll a (green)
and cyanin (blue)
•Most live in fresh water
•Some in salt water & soil
Starr, 315
Blue-green bacteria often link together,
forming “filaments”
Major producers in aquatic
ecosystems
Lichen - symbiotic organism of blue-green
bacteria and fungus
Some eubacteria are
chemosynthetic
Get energy by breaking down
inorganic compounds such as
ammonia, nitrite, or sulfur.
Live in sea water, fresh water,
and soil.
Nitrifying bacteria – change toxic
ammonia waste into nitrites and
nitrates, which plants can use.
Nitrobacter bacteria
Domain Archaea
Kingdom Archaebacteria
- “Ancient”, most primitive
earliest known form of life
-
differ chemically from Eubacteria
– Cell walls: eubacteria have peptidoglycan
Archaebacteria have other polysaccharides
- other molecules (enzymes, lipids) differ
Chemistry of Archae
• Different from bacteria
• Cell walls, enzymes, lipids
• More like that of Eukaryotes – like us!
Archae are extremophiles
Live in habitats like early earth
Too harsh for most organisms
1) methanogens – make methane: decomposers,
in animal intestines, swamps, treat sewage
2) Halophiles – salt
3) Thermophiles – hot
4) Acidophiles – acid
Acidophiles – live in acid pools
Archaea are Extremophiles
Halophiles – salt ponds, Great Salt Lake
Thermophiles – deep sea vents
Thermophiles – hot springs, geysers
Thermophiles live in this boiling pool in
Yellowstone Park
Notice the
gray path on
the left, and
people
walking on it
Grand Prismatic Basin, Yellowstone National Park
Some Archaea are Chemosynthetic
• Producers on ocean floor
• Inside giant tube worms
• Use heat and chemicals
from thermal vents to
make food
Human Uses for Bacteria
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•
•
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Food culture (yogurt, cheeses, vinegars)
Bioremediation (clean up poisons, oil spills)
Source for antibiotics (ex. Streptomycin)
Water treatment
Drug development
Medical, genetic research
Gene engineering
Some Bacterial Diseases
Salmonella
Strep throat
tetanus
tuberculosis
diptheria
MRSA
The Germ Theory of Disease
1800s
• Louis Pasteur - microscopic organisms
cause many human diseases
• Robert Koch - “Koch’s Postulates”: steps
to identify the organism causing an illness
• Joseph Lister – sterile technique
• Alexander Fleming- discovered penicillin
Pathogenic Bacteria
Many groups and types, but divided into
two classes by GRAM STAIN
Schraer
637
Gram positive
Purple
Killed by normal
antibiotics
Gram negative
Pink - Cell wall blocks stain
Harder to treat if
pathogenic
HOW do bacteria make us sick?
1) some make toxins that kill cells or
interfere with their function
• Botulism, salmonella, cholera
2) some kill cells directly
3) some reproduce so fast their numbers
interfere with organ function
How Bacteria Populations Grow!!
Bacterial Growth Curve (in Culture)
Why do they die out?
Run out of food, or wastes build up
Controlling Bacteria
1. Soap and water – removes microbes
2. Store food at low temperature
3. Use high temperature to kill bacteria
- cook food thoroughly
- wash dishes in hot water
- sterilize medical objects >100 C
Chemical controls for bacteria?
Antimicrobial Agents - slow bacterial growth
a) antiseptics – on living tissue (skin)
b) disinfectants – on nonliving surfaces
c) antibiotics – inside living organisms
- damage molecules needed when cells divide
- cell wall (penicillin); proteins (tetracycline)
What are prions?
Misfolded protein molecule that can cause disease
- no DNA (not a virus)
- they cause normal proteins to misfold
 loss of tissue/organ function  death
- ex. “Mad Cow Disease” (brain)
- Creutzchfeldt-Jakob Syndrome in humans
A misfolded protein
What are viroids?
•
•
•
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Circular pieces of RNA
No protein or membrane coat (not a virus)
Can cause disease, more often in plants
Only human example – hepatitis D
What are viruses?
1. Genetic material inside a protein coat
2. “Alive” only when inside a living cell
Adenovirus
Causes colds and flu
Tobacco Mosaic Virus
First one discovered
Virus traits of life
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Replicate
Organized; complex molecules
Change over time (mutate)
NOT CELLS
Known since 1800’s but too small
to see until electron microscope
discovered in 1930’s
Did you know? Viruses can be
as small as 30 nm.
Bacteriophage
Infects bacteria
Viral structure
Core - genetic material, DNA or RNA
Capsid - Protein coat
surface markers – protein spikes
Envelope - Some viruses
wrap in host cell membrane
- viral proteins stick through
membrane
How are viruses classified?
1) type of organism infected (animal, plant, bacteria)
2) type of nucleic acid (DNA or RNA)
3) shape (geometric, thread, rod…)
Tulip colors caused
by harmless virus
polyhedron
Ebola, thread-shape
How do viruses reproduce?
Viruses must
be INSIDE living
cells to reproduce.
They take over the
cell machinery to
make more virus
particles.
HIV virus
entering cell
Lytic Cycle
1. Virus binds
to host cell
2. Viral DNA
enters host cell
3. Virus destroys
host cell DNA
5. Host cell bursts;
new viruses infect
more cells
4. Host cell makes
new viruses
Lysogenic Cycle
Some viruses have a dormant stage
1. Viral DNA blends into
host DNA
2. When cell reproduces,
so does viral DNA
3. Later, a cell message
activates lytic cycle
What is a retrovirus?
• Can make DNA from its RNA. This DNA
blends into the host cell DNA
• forms a provirus
• Viral DNA may become
active later
Did you know?
AIDS
is caused by a retrovirus.
A retrovirus changes host cell DNA
Reverse transcriptase – enzyme makes DNA from RNA
How do viruses spread?
Viruses can be spread by:
• air, water, food, insects
• other people (body fluids: saliva, blood,
semen)
• Some can stay dormant on contaminated
surfaces for years!!!
Some Human Disease Viruses
measles
Hepatitis
herpes
Chicken pox
Polio
flu
Other things that make us sick!
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Genes – ex. Cystic Fibrosis
Fungi – ex. athlete’s foot
Protozoans – ex. Malaria
Animal parasites – ex. tapeworm
Environmental pollutants
Body’s Defense against Disease
1st line of defense: physical barriers
- skin, mucous membranes, tears,
stomach acid
2nd line: Inflammation
a. chemical messages
b. white blood cells - phagocytes
3rd line: Immune Response
a. white blood cells and antibodies
Inflammation
Immune Response: B and T white
blood cells target invaders
• Lymphocyte – type of white blood cell
• Antigen – anything that causes an immune response
– Usually a surface protein on a foreign particle
• B lymphocytes make antibodies :
– Proteins, specific for an antigen
– Bind antigens, makes destruction easier
How
antibodies
work
Other B and T cells
Memory cells -
remember invader, so body
can react fast if same invader comes back again
Killer T cells – cytotoxic cells; kill invaders
Helper T cells – label invaders for
destruction; alert and coordinate immune
response
How do immune cells fight disease?
Killer T cells attack a cancer cell
Role of Helper T cells
Why HIV stops immunity
• HIV virus attacks helper T cells
– Without labeling by helper T cells, other
immune cells do not recognize pathogen
as foreign
– No response
Fighting Infections
Immunity – resistance to an infection
a) active immunity – immune system fights an
infection and remembers the invader
primary: vaccinations, illnesses  memory cells
secondary: fast defense if invader returns
b) passive immunity - white cells, antibodies
from another person to resist a current infection
ex. Mother-to-fetus, serums, injections of
antibodies (no memory cells!)
Drugs that slow viral replication
1) Antiviral drugs – slow reproduction (ex. Tamiflu)
2) Interferon – protein made by virus-infected cells
- sent to neighboring cells
- “interferes with” viral reproduction
3) Antibiotics DO NOT work on a virus
- virus hides inside a living cell
Even Bacteria have defenses!
• Bacteria make Restriction Enzymes
– Cells infected with phage virus send distress
signals to nearby cells
– These cells make enzymes that cut up viral
DNA
“Restricted” – cut at a
specific base sequence
Vaccines
Made from dead or weakened virus
- Prime immune system to recognize a
virus and respond quickly
1798 Edward Jenner – smallpox
1884 Louis Pasteur – rabies
1954 Jonas Salk – polio, injected
1960 Albert Sabin – polio, oral
Gene therapy using viruses
More photosynthetics
2) green-sulfur and purple bacteria
- anaerobic
- colors range from pink to black
- photosynthesize without water
- make no oxygen
- live in pond and sea mud
Protein Synthesis in Cells
In normal cells: DNA contains code
- code is written on RNA molecule
- RNA goes to ribosome to make a protein
Protein synthesis in Viruses
DNA viruses: work like a cell
• DNA enters cell -their code is written on
RNA - make proteins
3) RNA viruses - make proteins